Remarks

This class implements a map (the IMap; interface) with keys of type String and values of type PropertyValue. The PropertySet type enables various Windows Runtime APIs to return a collection of mixed values that can still be iterated or inspected using the common collection APIs of PropertySet, which match those of IMap;, IDictionary<TKey,TValue>, or JavaScript collection and enumeration techniques, depending on which language your app uses.

PropertyValue is a class that supports a large number of static Create* methods that create a deliberately untyped value from an input that's typically a value type or primitive (Boolean, numbers and so on) or an array of those values. Once one of the static PropertyValue methods is called, its return value can be treated as a PropertyValue instance (however the Create* methods technically return an Object if you look at the signatures).

However, you don't typically use a PropertySet in a way that requires you to fill the PropertyValue values in the set yourself. Instead, you typically get a filled-in PropertySet as a return value from a Windows Runtime API that's providing a collection where the value types within it might be mixed, but are still related to each other by origin or scenario. For example, the LocalSettings and RoamingSettings values that you get when you retrieve app data are of type ApplicationDataContainer, and each contains a PropertySet as its Values property value. When you interact with app data that's storing settings, you typically get the collection from ApplicationDataContainer.Values. Then you can:

use Lookup or the Item indexer to retrieve an item once you know it exists

For scenarios like working with app data, when you have a PropertySet you have it by reference, so if you add items to the PropertySet using Add/Insert these items will be added to the app data, and removing items removes them from app data. All such changes are then shared through the app data mechanisms, if they're made to the RoamingSettings.

Various properties that report info from media and devices use PropertySet, for example PlayToReceiver.Properties. However, there are other media/devices property sets that don't use PropertySet and instead use MediaPropertySet, because the identifier for those properties is better represented when keyed as a GUID rather than a string.